In manufacturing semiconductor devices, resist patterns have been required to be made minute enough to meet increased integration density and highly accelerated processing speed in LSIs. Resist patterns are normally formed in photo-lithographic processes from, for example, positive-working type resists, whose solubility to alkaline developers are increased by exposure to light. Accordingly, the resists in the areas exposed to light are removed away with the alkaline developers to form positive resist patterns. However, the fineness of the resultant patterns greatly depends on the exposure methods and light sources, and hence in order to stably produce fine resist patterns, a huge investment is necessary to install special and expensive facilities and equipment needed for the exposure methods and light sources capable of ensuring the fineness.
In view of that, there are various techniques studied for further miniaturizing resist patterns formed beforehand by conventional methods. For example, they include a practical method in which a resist pattern stably produced by a conventional method is coated with a composition comprising a water-soluble resin and optional additives so as to fatten or thicken the resist pattern and thereby to reduce the diameter of holes and/or the width of furrow lines separating the ridges in the pattern.
The composition containing a polymer comprising a repeating unit with nitrogen is known to interact with residual acid in the resist pattern to fatten the resist pattern and to form a desired fine space pattern (US 2006/0088788 A1, Japanese Patent Application Laid Open (JP-A) No. 2013-83818). Furthermore, a nitrogen heteroaromatic ring unit in the polymer of the composition is known to improve a dry etching resistance of the resist pattern (Japanese Patent Application Laid Open (JP-A) No. 2003-84457).
However, the composition of aqueous solution has an issue on coatability. Surfactant is inevitable for the composition to come into use. Moreover, the type of chemical agents that can be linked to a coater/developer track to be used in semiconductor process at present is limited to resist materials and rinse solutions, and it is very difficult to set up a new process line for a new chemical agent. In the conventional semiconductor process, it is not based on the assumption that an aqueous solution material is applied over a surface of a resist pattern, and thus it is also difficult to use such an aqueous solution material because of the necessity of a new control for waste fluid.
With the use of an organic solvent composition using novolac resin or p-hydroxystyrene-styrene copolymer described in Japanese Patent Application Laid Open (JP-A) No. 2013-145290, it has been known that the use of the organic solvent composition is not sufficient in thickening a negative-tone resist pattern.